1. Technical Field of the Invention
This invention relates generally to pressure jacket systems for securing a syringe to an injector, to syringes for use with pressure jacket systems, and to methods of loading syringes in and removing syringes from pressure jacket systems. More specifically, the invention relates to front-loading pressure jacket systems and methods for allowing front loading and removal of syringes therefrom, and to syringes of special construction for use with, for example, pressure jackets.
2. Description of Related Art
In the medical field, patients are often injected with fluids in procedures such as angiography, computed tomography (CT), and magnetic resonance imaging (MRI). In such procedures, which require controlled injection of relatively large volumes of fluid into a patient, a catheter is used as a conduit for the fluid, which is connected to the syringe(s) by a connector tube. The syringe(s) is mounted on a motorized injector having an injector head. For compatibility with injectable fluids, syringes may be made of glass or polymeric materials, such as polypropylene, with a certain minimum wall thickness. The thickness is critical as typical pressures of up to 1200 p.s.i. (i.e., in angiographic procedures) are used to inject the fluids into a patient.
Pressure jackets are known in the art in at least two varieties, breech or rear loading and front loading, for substantially enclosing and retaining syringes while in use. A pressure jacket serves to limit radial expansion of a syringe, which may lead to bursting or to leaks of the pressurized fluid around the seal(s) of the syringe plunger. Another function of a pressure jacket is to prevent forward motion of the syringe. For example, a force of 2400 pounds is typically required to restrain the forward motion of a 150 ml syringe with a cross section of 2.0 in2 at 1200 p.s.i.
U.S. Pat. No. 4,677,980, the contents of which are incorporated herein by reference, discloses an angiographic injector apparatus in which syringes are rear loaded into a pressure jacket of the injector. More specifically, the apparatus comprises a rotatable turret that carries a pair of the pressure jackets and which is rotatable so that when one of the pressure jackets, into which a syringe has been rear loaded, is in an injection position, the other pressure jacket is in a position in which an associated syringe may be rear loaded. Subsequently, when injection of contrast media from the first syringe is completed, the turret is rotated to move the first syringe to an unloading-loading position, with the second pressure jacket and the second syringe concurrently being moved into the injection position.
A disadvantage of rear loading pressure jacketed injectors is that, after an injection, the patient tubing typically must be disconnected from the syringe before the syringe may be extracted from the rear of the pressure jacket and discarded. Not only does this operation expend valuable operator time but fluids, such as contrast fluid and blood, may drip or spill from the syringe or the tubing after the tubing is removed from the syringe thereby creating a potentially unsafe or hazardous condition. Additionally, fluid spilled during loading and purging of air from the syringe may migrate inside the pressure jacket and the injector and require cleaning.
Motivated at least in part by this concern, front-loading injectors (pressure jacketed and non-pressure jacketed injectors) have been developed. U.S. Pat. Nos. 5,300,031; 5,779,675; and 5,800,397, for example, disclose front-loading pressure jacketed injector systems and U.S. Pat. No. 5,383,858 discloses front-loading pressure jacketed and non-pressure jacketed injector systems. The contents of U.S. Pat. Nos. 5,300,031; 5,779,675; 5,800,397; and 5,383,858 are incorporated herein by reference.
U.S. Pat. No. 5,300,031 discloses various embodiments of a pressure jacketed injector system wherein a syringe is loaded into and removed from an injector pressure jacket through an opening provided in the front end of the pressure jacket. To retain the syringe within the pressure jacket, for example during an injection operation, the front end of the syringe is locked to the front end of the pressure jacket.
U.S. Pat. No. 5,779,675 also discloses various embodiments of front-loading pressure jacketed injector systems. In a number of embodiments, for example as shown in FIGS. 12-16 of the '675 patent, one or more retaining plates or walls preferably supported by one or more arms or rods retain a syringe within the pressure jacket. The retaining plates or walls are preferably moved between open and closed positions to allow syringes to be inserted into and removed from the pressure jackets.
While front-loading pressure jacketed injector systems are known in the art, improvements in the design of such pressure jacketed injector systems and also in the design of syringes used in both pressure jacketed and non-pressure jacketed injector systems are and continue to be highly desirable.